Due to a platform issue, elevated application packages occasionally fail
to find all of their dependencies. The real fix for this is going to
take a lot of time and probably a new build of Windows.
The fix we have here switches us to a non-"release" build of
Microsoft.UI.Xaml. The critical thing about their non-release builds is
that they prefer to embed their DLLs into the hosting package instead of
expressing a platform dependency.
This build of Microsoft.UI.Xaml was produced from the same commit as
the original and official build; the only difference is that it will
embed into our package.
Fixes#3275.
06f2706c40